Understanding big accidents
2. NASA's failing grade
3. The blame game
4. Accidents: Normal?
5. Holey-headed reactor
The Davis-Besse nuclear reactor is owned
by FirstEnergy, also implicated in the blackout of 2003. With a
major hole in its head, Davis-Besse has been idle for 19 months.
County Emergency Management.
In a pressurized water reactor, like Davis-Besse,
high-pressure water transfers heat. At Davis-Besse, water leaking
from inside the reactor vessel caused severe corrosion (arrow) in
the reactor head. The consequences of a major leak are uncertain,
but the Nuclear Regulatory Commission didn't want to find out.
Nuclear Regulatory Commission
Investigations into the recent blackout have
pointed to problems early in the day on Ohio transmission lines
owned by FirstEnergy Corp. As The Why Files goes to press, we read
that problems surfaced even earlier at an Indiana plant.
Curiously, FirstEnergy also owns the troubled Davis-Besse nuclear plant, which has been idle for more than
570 days running -- longer, even, than the plant's previous record,
Davis-Besse has, in technical terms, a hole in the head left by the corrosion of almost six inches
of solid steel. When the reactor was finally shut down, the weakest
link in the highly pressurized reactor vessel was a 3/16th-inch
And while Davis-Besse was not, technically,
an accident because it did shut down safely, one way to learn about
accidents is to examine near-misses, AKA accidents-waiting-to-happen.
The immediate cause of the corrosion was a
leak of acidic water from inside the reactor. But that was no surprise,
says Vicki Bier, a nuclear-safety specialist at the University of
Wisconsin-Madison. Corrosion "was a known problem -- plants were
required to have a corrosion control program, and Davis had one
like everyone else."
An accident was averted due more to luck than
to the corrosion control program, says Bier, who sees plenty of
symptoms of those familiar culture problems at Davis-Besse:
The context: Similar reactors don't have
the same holes.
The time scale: "Corrosion is a slow problem that
went on for many years, with many people involved in the whole
inspection process," Bier says. "It was not a one-time mistake."
The failed fix: Instead of inspecting for
corrosion, Bier says, "They would blast the reactor head with
a high-pressure hose ... and say they had done the corrosion program...
they went through the motions and checked it off their list."
Unfortunately, the corrosion was hidden by
deposits of boric acid that had leaked from the reactor vessel,
and the reactor had to be shut down for safety violations. As we
write, a replacement reactor head is being installed.
Don't make the mistake of ignoring
our accidental bibliography...